000031891 001__ 31891
000031891 005__ 20180501105743.0
000031891 0247_ $$2doi$$a10.5075/epfl-thesis-1413
000031891 02471 $$2nebis$$a1521831
000031891 037__ $$aTHESIS_LIB
000031891 041__ $$aeng
000031891 088__ $$a1413
000031891 245__ $$aConsolidation mechanisms and interfacial phenomena in thermoplastic powder impregnated composites
000031891 260__ $$aLausanne$$bEPFL$$c1995
000031891 269__ $$a1995
000031891 300__ $$a153
000031891 336__ $$aTheses
000031891 520__ $$aThermoplastic powder impregnation of continuous       reinforcement filaments is studied in this work, focusing on       impregnation mechanisms and interfacial phenomena. Various       existing techniques to mingle powdered resins to continuous       filaments are reviewed; a powder impregnation line designed       at the Laboratoire de Technologie des Composites et       Polymères (LTC) is presented. Two important types of       powder coated towpregs are addressed: FIT bundles       (Fibres Imprégnées de Thermoplastique) of       powder loaded fibres enclosed in a thin resin sheath, and       molten powder towpregs in which the particles are       fixed to the fibres in an oven by melting the resin. The impregnation mechanisms of powder coated towpregs are       examined. The formation of resin bridges between adjacent       fibres is first investigated using a hot stage placed on a       microscope. In the absence of externally applied pressure,       impregnation is driven by surface energy effects. The driving       forces leading to the spreading of the bridge along the       fibres are analysed at two levels: at a macroscopic scale,       characterising the capillary pressure governing the flow of a       liquid into a porous solid, and at a micro-mechanical level       analysing the capillary forces in a system defined by a       liquid drop in contact with two solid particles. To achieve impregnation at a satisfactory rate, however,       it is essential to apply external pressure to most       thermoplastic systems during consolidation. An analytical       model for the consolidation stage of unidirectional-powder       coated towpregs is presented, placing in context effects due       to surface energy, viscous flow, externally applied pressure       and fibre bed elasticity. The initial conditions for the       computation depend on the impregnation technique used. FIT       bundles, and molten powder towpregs are examined. The       model is compared at each stage to experimental data obtained       by compression moulding powder impregnated towpregs in an       instrumented hydraulic press using a closed matched-die       mould. This model optimises the processing conditions of a       given fibre-resin system to achieve a void free laminate with       improved mechanical properties. Mechanical properties can further be improved by       optimising interfacial adhesion between resin and fibres.       Surface energy effects on composite mechanical properties are       studied, relating thermodynamic quantities to adhesive       strength. A criterion for optimum adhesion is proposed. The       influence of the thermodynamic adhesion between fibres and       matrix on the mechanical properties of a continuous fibre       reinforced composite is studied for two systems: carbon fibre       reinforced poly(ether-ether-ketone) and glass fibre       reinforced poly(ether-imide). The fibre surface is modified       chemically and characterised by optical contact angle       measurements of molten resin droplets on the fibres.       Unidirectional fibre reinforced laminates are manufactured.       Transverse flexural strength is reported as a function of       thermodynamic wetting parameters. Adhesion at the fibre-resin       interface is found to correlate with both composite strength       and void morphology within the laminate after       consolidation. Full potential of powder coated towpregs as a precursor       for compression moulded composite parts can be reached by the       fabrication of drapeable textile preforms. Corrugated sheets       are processed usign FIT woven fabrics. Mechanical property       measurements show that complex high quality parts can be       processed at high rates using powder coated towpregs.
000031891 700__ $$aConnor, Marco Tom
000031891 720_2 $$aMånson, Jan-Anders E.$$edir.
000031891 8564_ $$s8747428$$uhttps://infoscience.epfl.ch/record/31891/files/EPFL_TH1413.pdf$$yTexte intégral / Full text$$zTexte intégral / Full text
000031891 909CO $$ooai:infoscience.tind.io:31891$$pDOI2$$pDOI$$pthesis
000031891 920__ $$b1995
000031891 970__ $$a1413/THESES
000031891 973__ $$aEPFL$$sPUBLISHED
000031891 980__ $$aTHESIS